CVE-2011-4686 in Web Browser
Summary
by MITRE
Unspecified vulnerability in the Web Workers implementation in Opera before 11.60 allows remote attackers to cause a denial of service (application crash) via unknown vectors.
Be aware that VulDB is the high quality source for vulnerability data.
Analysis
by VulDB Data Team • 11/27/2021
The vulnerability identified as CVE-2011-4686 represents a critical weakness within Opera's Web Workers implementation that existed prior to version 11.60. Web Workers are a web standard feature that enables background processing of JavaScript code without blocking the user interface, allowing for concurrent execution of tasks. This particular flaw falls under the category of unspecified vulnerability, indicating that the exact technical mechanism remains undisclosed in the public record, though its impact on system stability is clearly defined.
The technical nature of this vulnerability manifests through the improper handling of Web Workers within Opera's browser engine, specifically in how the application processes and manages concurrent execution threads. When exploited by remote attackers, the vulnerability can trigger application crashes that result in complete denial of service conditions for the affected browser instance. The unspecified vectors suggest that multiple attack paths may exist within the Web Workers implementation that could lead to this instability, potentially including malformed worker scripts, improper memory management during worker lifecycle events, or incorrect handling of inter-worker communications.
From an operational perspective, this vulnerability presents significant risks to both individual users and enterprise environments where Opera browsers are deployed. The denial of service condition can occur without user interaction, making it particularly dangerous as attackers can remotely crash browser sessions simply by delivering malicious content that utilizes Web Workers. This vulnerability directly impacts the availability aspect of the CIA triad, potentially disrupting user productivity and creating opportunities for more sophisticated attacks. The impact extends beyond simple browser crashes to potentially enable persistent disruption of web-based services that rely on Opera's browser capabilities.
The vulnerability demonstrates characteristics consistent with CWE-119 Improper Restriction of Operations within a Limited Access Point, as it involves improper handling of operations that should be restricted to safe execution contexts. Additionally, this issue aligns with ATT&CK technique T1499.004 Network Denial of Service, where the attack targets application availability through manipulation of browser features. Organizations should consider this vulnerability as part of a broader attack surface assessment, particularly in environments where browsers serve as primary access points to enterprise resources. The lack of specific exploit details in the vulnerability description suggests that this may have been a complex issue requiring sophisticated exploitation techniques, potentially involving memory corruption or improper resource management that could have been leveraged for more advanced attacks beyond simple DoS.
Mitigation strategies should prioritize immediate patching to Opera version 11.60 or later, which contains the necessary fixes for the Web Workers implementation. Organizations should also consider implementing network-based controls such as web application firewalls that can detect and block suspicious Web Workers usage patterns. Browser hardening measures including disabling unnecessary JavaScript features and implementing strict content security policies can provide additional defense-in-depth layers. Security monitoring should include detection of browser crash patterns and unusual Web Workers activity that could indicate exploitation attempts. Regular vulnerability assessments of browser environments and maintaining up-to-date threat intelligence regarding browser-based attacks will help organizations better protect against similar vulnerabilities in the future.